Apparatus that comprises an optical assembly [we intend "optical assembly" to include assemblies that comprise opto-electronic elements such as optical radiation detectors (e.g., PIN diodes), or optical sources (e.g., LEDs or laser diodes), assemblies that comprise only purely optical elements, as well as assemblies that comprise optical and opto-electronic elements], finds use in many important fields of technology, e.g., in optical communications, and is expected to find even wider use in the future, e.g., in optical computing. In many of these fields reliability of the optical assembly is of utmost importance. One known technique for achieving high reliability comprises placement of the optical and/or electro-optical components into a controlled environment, namely, into a sealed housing. This application deals with sealed optical assemblies comprising means for coupling an optical fiber to an optical or opto-electronic device.
Sealed optical assemblies of the relevant type are well known to the art. However, such prior art assemblies generally have one or more shortcomings. Among these shortcomings are complex design and/or assembly, relatively high cost, limited flexibility with regard to product code changes, a relatively high number of critical (i.e., leak-tight) seals, need for metalized fiber, use of precision-machined parts, and need for active alignment of the device relative to the fiber.
For instance, in one type of sealed assembly, exemplified by U.S. Pat. No. 4,119,363, the fiber (frequently a metal-coated fiber) is threaded through a metal tube, a solder seal is formed between the fiber and the tube, the tube is inserted into a metal housing and soldered thereto, after active alignment of the fiber to a device within the housing. It will be noticed that such an assembly comprises two critical seals, namely, the solder joint between the tube and the housing, and the solder joint between the tube and the optical fiber. The reliability of the latter joint typically is highest if the fiber is metalized. Such metalization however is relatively costly, and frequently results in reduced fiber strength. Another example of this type of sealed assembly can be found in U.S. Pat. No. 4,719,358.
A second type of sealed assembly is exemplified by U.S. Pat. No. 4,222,629. In this type of assembly the fiber is not brought inside the sealed assembly, and thus the need of forming a leak-thigh seal between fiber and another member is eliminated. The '629 patent discloses a precision member that is soldered into an aperture in the assembly housing and which receives a mating body with the fiber therein. A transparent face plate is soldered into the end face of the precision member, such that light from the fiber is transmitted through the face plate and can be detected by a detector inside the sealed assembly. The detector is actively aligned with respect to the fiber. The connector of the '629 patent comprises a precision machined part which determines all critical alignment dimensions, and two critical seals, namely, the joint between the precision member and the assembly housing, and that between the face plate and the end face of the precision member. Furthermore, the design requires active alignment, namely, visual positioning of the device with respect to the fiber.
In view of the commercial significance of sealed optical assemblies, it would by highly desirable to have available an assembly that can have a smaller number of critical seals than do prior art assemblies, that does not require a precision machined member for coupling the fiber to the assembly, that does not require metalized fiber, and the optionally can be assembled without active alignment of the fiber relative to a device within the housing of the assembly. This application discloses assemblies having one or more of these characteristics.